By taking a little more Botox than that used for wrinkles can significantly reduce patients' upper limb shaking, a Royal Melbourne Hospital study has found.

Botox, a toxin derived from the Clostridium botulinum germ, is a muscle-relaxing medication used by the cosmetics industry to smooth wrinkles but it also has a number of medical benefits.

It has already proven effective for muscle stiffness experienced by multiple sclerosis patients and is also available as a treatment for stroke and cerebral palsy sufferers.

Neurologist Anneke Van Der Walt and her team tested Botox in 23 patients, with all the patients experiencing a reduction of about 40 per cent in the severity of their shaking. Writing and drawing abilities improved by about 30 per cent in most patients, Van Der Walt said adding overall, patients experienced improvements across a range of everyday activities.

"Even though it is a small study the results are very significant," Van Der Walt was quoted as saying by the Australian news agency AAP.

"We feel that this gives us a platform now to test this in more patients. Hopefully this will translate into a very significant treatment for patients with MS who have this shaking of the upper limbs," she said.

Van Der Walt said Botox could be injected every three to four months but the study found most patients only required it every six months.

"Every person and their tremor is different and doses, and timing of the doses, need to be individualised," she said.

About two-thirds of MS patients suffer upper limb tremors. However, the main side effect of the Botox treatment is said to be muscle weakness, which often dissipates after one to two weeks, the neurologist said.

A patient in the trial, 62-year-old Anca Chernok, said the tremors she experienced forced her to stop working 12 years ago. She said the Botox treatments in her arms allowed her to care for herself. "To be self sufficient, to look after myself ...Was a great gift," she said.

"I felt human again." Another patient, Andrew White, 55, said the treatments had allowed him to continue working as a human relations manager and to help around the house.

"My wife is delighted that I don't smash dishes anymore when I'm putting them in the dishwasher," he joked. Both patients have continued receiving the injections outside of the trial. The treatment will be trialled among a larger number of patients next year.